Targeted cancer therapy is designed to disrupt the function of specific molecules needed for carcinogenesis and tumor growth and thus either kills or prevents the growth of cancer cells (Ji H et al (2006) Cell Cycle 5(18):2072-2076 Epub 2006 Sep. 15). In contrast to conventional cytotoxic chemotherapy, such targeted cancer therapies may be more effective and less harmful to normal cells. A main effort in the targeted cancer therapy field has been the development of agents that target the epidermal growth factor receptor (EGFR). EGFR is a member of the ErbB family of closely related receptors including EGFR (ErbB-1), Her2/neu (ErbB-2), Her3 (ErbB-3) and Her4 (ErbB-4). Activation of EGFR leads to receptor tyrosine kinase activation and a series of downstream signaling events that mediate cellular proliferation, motility, adhesion, invasion, and resistance to chemotherapy as well as inhibition of apoptosis, processes that are crucial to the continual proliferation and survival of cancer cells.
As expression of the EGFR vIII mutant receptor is restricted to tumor cells, it represents a highly specific target for antibody therapy. Accordingly, both polyclonal and monoclonal antibodies specific to the unique peptide of de2-7 EGFR have been generated. A series of mouse mAbs, isolated following immunization with the unique de2-7 peptide, all showed selectivity and specificity for the truncated receptor and targeted de2-7 EGFR positive xenografts grown in nude mice (Wikstrand C J et al (1995) Cancer Res 55:3140-3148; Okamoto, S et al (1996) Br J Cancer 73:1366-1372; Hills D et al (1995) Int J Cancer 63:537-543; Reist C J et al (1997) Cancer Res 57:1510-1515; Reist C J et al (1995) Cancer Res 55:4375-4382; U.S. Pat. No. 5,401,828). Examples of anti-EGFR vIII antibodies include ABX-EGF (panitumumab), DH8.3, L8A.4, and Y10.
MAb806 is a novel murine antibody, originally raised to recognize the unique truncation mutant, EGFRvIII using whole cells expressing EGFR vIII mutant as immunogen. Importantly, the epitope recognized by mAb806 is not accessible in inactive wild-type (wt) EGFR, but is exposed in a transitional form of wt EGFR in cells with overexpression of EGFR, and expression of EGFRvIII. MAb806 binds to an epitope present or available in the EGFRvIII/Δ2-7 EGFR mutant, but recognizes an epitope distinct from the mutant's junctional peptide LEEKKGNYVVTDH. The epitope studies are supported by immunohistochemical studies demonstrating that the 806 antibody binds to epitopes present in gliomas, as well as a broad range of epithelial cancers, but not to normal human tissues. These and other preclinical data suggest that mAb806 might have a different spectrum of clinical activity and side effect profile distinct from cetuximab and other anti-EGFR antibodies. In xenograft models, mAb806 has exhibited a potent anti-tumor activity with no targeting of normal tissues. Thus, the unique targeting capabilities of mAb806 represent a new paradigm for cancer-specific molecularly targeted therapy.
The non-receptor protein tyrosine, Src, is a 60-kDa protein that is a member of a nine-gene family, including Src, Yes, Fyn, Lyn, Lck, Hck, Fgr, Blk, and Yrk, that plays a critical role in the regulation of many cellular processes, such as proliferation, differentiation, migration, adhesion, invasion, angiogenesis, and immune function (Yeatman T J. (2004) Nat Rev Cancer 4(6):470-80; Frame M C. (2004) J Cell Sci 117:989-98). The Src family kinase contains a poorly conserved domain and three conserved Src homology domains: SH2, SH3, and SH1 or protein tyrosine kinase domain. Critical to the regulation of Src is a COOH-terminal tyrosine (Y530) that, when phosphorylated by C-terminal Src kinase (Csk), leads to a more inactive Src conformation. Src interacts with many proteins, depending on the input signal. It further assumes its active conformation through dephosphorylation of Y530 and autophosphorylation of Y418. Src also associates with structural and signaling proteins, and the resulting complexes are critical to Src's role in diverse cellular processes. Src has been reported to be overexpressed or aberrantly activated in a number of cancers, such as colon, breast, melanomas, ovarian cancer, gastric cancer, head and neck cancers, pancreatic cancer, lung cancer, brain cancers, and blood cancers (Dehm S M and Bonham K (2004) Biochem Cell Biol 2004; 82:263-74). There are several known small molecule inhibitors of src and some have entered clinical trials, for example dasatinib (BMS354825), AZD-0530, SKI-606, PP1 (4-Amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]-pyrimidine), PP2 (4-chlorophenyl)-7-O-butyl)pyrazolo[3,4-d]-pyrimidine), PD166326.
There is a clinical need for enhanced, more efficacious and more broadly effective treatment protocols for EGFR-mediated disease including cancer.
The citation of references herein shall not be construed as an admission that such is prior art to the present invention.